Aurora, Colo. police used surveillance cameras to scan 12 million vehicle license plates last year.
Eight cameras mounted atop stoplights throughout the city as well as scanners on 11 police cruisers are used to capture the license plate, as well as a photo of the vehicle. KMGH-TV reported the collection of plates has resulted in 322,000 alerts of stolen vehicles or wanted suspects.
Lt. Dan Mark says the department recovers an average of two to three stolen cars per week because of the system. Mark says the photos are kept for 18 months, while the plate number is kept for two years.
The American Civil Liberties Union has raised privacy concerns. The ACLU says the cameras are also used in other cities including Boulder, Longmont, Lafayette, Erie, Louisville, and Thornton.